A conventional antenna disclosed in Patent Literature 1 includes a splitter circuit and a pair of antenna elements spaced apart from each other in order to transmit and/or receive electric waves from all directions at high levels. The splitter circuit of the antenna in Patent Literature 1 includes input terminals that receive signals and are connected to the antenna elements via a branched line split in two segments. The antenna includes another line and a delaying circuit that are connected in parallel between one end of the branched line and the antenna element connected to the end of the branched line. The antenna also includes two switching circuits switching between the line and the delaying circuit. The switching circuits are switched to transmit, to one of the antenna elements, a signal with the same phase as or with a phase different from that of the other antenna element. The directivity is varied in such a simple configuration.